Recovery of yttrium and neodymium from copper pregnant leach solutions by solvent extraction

The solvent extraction of yttrium and neodymium from copper pregnant leach solutions (PLS) using Primene JM-T, a primary aliphatic amine, has been studied. Effect of contact time, pH, sulfate concentration, and extractant concentration were investigated using synthetic and actual PLS systems. Standard experimental conditions were 5 min contact time, pH ~ 2.5, 10 % v/v Primene JM-T concentration, and 1:1 O:A phase ratio. Distribution isotherms were constructed for the pure systems and for actual copper leach solutions. Synthetic solutions contained 100 ppm Y and ~75 ppm Nd. Copper PLS contained 14.9 ppm Y and 2.1 ppm Y. Results showed that complete extraction of both yttrium and neodymium occurred within 5 min and at pH values greater than 1. It was also found that sulfate concentration does not inhibit extraction at any concentration. Using synthetic solutions of yttrium and neodymium, it was found that the reaction stoichiometry requires 2 moles of Primene JM-T per mole of metal extracted. This suggests that a both bi-sulfate and tri-sulfate complexes are being extraction. For the copper bearing PLS, 3 moles of Primene JM-T were required per mole of metal extracted. This support the tri-sulfate complex as being the predominate species being extracted.